Chemistry for Kids: Elements - The Noble Gases Elements for Kids Noble Gases The noble gases are a group of elements in the periodic table. They are located to the far right of the periodic table and make up the eighteenth column. Elements in the noble gas family have atoms with a full outer shell of electrons. They are also called the inert gases. What elements are noble gases? The elements that make up the family of noble gases include helium , neon , argon , krypton, xenon, and radon. What are the similar properties of noble gases? Noble gases share many similar properties including: A full outer shell of electrons. Helium has two electrons in its outer shell and the rest have eight electrons. Because of their full outer shells, they are very inert and stable. This means they don't tend to react with other elements to form compounds. They are gases under standard conditions. They are colorless and odorless. Their melting and boiling points are close together giving them a very narrow liquid range. Abundance Helium is the second most abundant element in the universe after hydrogen. Helium makes up about 24% of the mass of the elements in the universe.

Neon is the fifth most abundant and argon is the eleventh. On Earth, the noble gases are fairly rare with the exception of argon. Argon makes up just under 1% of the Earth's atmosphere, making it the third most abundant gas in the atmosphere after nitrogen and oxygen. Interesting Facts about Noble Gases Because helium is non-flammable it is much safer to use in balloons than hydrogen. Krypton gets its name from the Greek word "kryptos" meaning "the hidden one." Many of the noble gases were either discovered or isolated by Scottish chemist Sir William Ramsay. Helium has the lowest melting and boiling points of any substance. All of the noble gases except for radon have stable isotopes. Neon signs do not use just neon gas, but a mixture of different noble gases and other elements to create bright lights of different colors. Noble gases are often used to create a safe or inert atmosphere due to their stable nature.

Xenon gets its name from the Greek word "xenos" which means "stranger or foreigner." More on the Elements and the Periodic Table List of Noble Gases | eHow List of Noble Gases neon sign image by pearlguy from Fotolia.com The six noble gases are all found in group 18 of the periodic table. Noble gases are different from other elements because they have a full set of electrons in their outer shell. Most gases have too few or too many. This complete electron shell makes noble gases very stable, a fact that once saw them referred to as "inert gases." However, some of the noble gases are now known to take part in chemical reactions. Helium Helium has an atomic number of 2 and is represented by the symbol He. The gas was discovered in 1895, but, according to the BBC website, its existence had been previously proposed by Pierre Jules Cesar and Sir Joseph Norman Lockyer. The two men that named the gas "helium" after the Greek word for sun. Helium is often used in balloons due to its lighter than air properties. It is also used in deep sea diving equipment to dilute a diver's oxygen supply.

Neon Neon has an atomic number of 10 and the symbol Ne. It was discovered in 1898 by two British chemists, William Ramsay and Morris W. Travers, and named after the Greek word for new, "neos." Neon is often used in lighting and fluorescent signs. The gas itself is colorless but glows in an electric discharge. Argon Argon has an atomic number of 18 and the symbol Ar. It was isolated in 1894 by Lord Rayleigh and William Ramsay, becoming the first of the noble gases to be discovered. The stable nature of the gas earned it the name "argon," the Greek word for inert. According to the Royal Society of Chemistry website, "Argon is widely used to provide an inert atmosphere for high-temperature metallurgical processes." Like neon, it is also used in lighting. Krypton Krypton is represented by the symbol Kr and has an atomic number of 36. Krypton was discovered in 1898 by William Ramsay and Morris W. Travers, just a few weeks before they discovered neon. It was named after the Greek word "kryptos," meaning hidden.

The gas is used in fluorescent lighting and in various types of photographic flash bulbs. Xenon Xenon has an atomic number of 54 and the symbol Xe. It was discovered by Ramsey and Travers in 1898, shortly after their discovery of neon and krypton, and named after the Greek word for stranger. Xenon is found naturally in the atmosphere, but only in minute quantities. According to the PeriodicTable.org website, xenon is used in photographic flashes, general anesthetic and stroboscopic, bactericidal, and laser-pumping lamps. Radon Radon, the last noble gas to be isolated, has an atomic number of 86 and the symbol Rn. It was initially observed in the 1890s before being isolated by Friedrich Ernst Dorn in 1900. It was properly classified in 1908 by William Ramsay. Radon is colorless, odorless, tasteless and, unlike the other noble gases, radioactive. It occurs naturally from decaying radium and is considered hazardous due to its radioactivity. It is used in radiotherapy for the treatment of cancer.

The Elements: Noble Gases The Noble Gases With a name taken from the Greek helios for "sun", helium is the second lightest and second most abundant gas in the known universe (hydrogen being number one). Because of its scarcity in our atmosphere its existence was not suspected until spectroscopic measurements revealed an unknown element present in the sun. The discovery of helium is generally credited to Janssen and Lockyear in 1868. As no helium compounds are known, this family of gases was once thought to be inert. In 1962 the first noble gas compound was prepared with xenon (see below). Still, helium only occurs in uncombined form and must either be extracted from the atmosphere by liquefaction of air or separated from deposits of natural gas. It is thought that some of the terrestrial helium is the product of the alpha decay of radioactive isotopes beneath the crust. Helium is the only known element which cannot be converted to a solid simply by cooling. It has 98% the lifting power of hydrogen with none of the Hindenburg-type drawbacks, and is still used today in airships.

Additional Information About Helium The fourth most abundant element in the known universe, neon was discovered in 1898 by Ramsay and Travers. Its name is taken from the Greek neos or "new". This is perhaps the best known noble gas because of its use in so-called "neon" lights (many of which actually contain other gases) and is relatively plentiful in the earth's atmosphere (fifth in abundance, following carbon dioxide). No stable compounds of neon are known to date. The gas is extracted from air by liquefaction. Additional Information About Neon Argon is third in abundance in the earth's atmosphere (about 1% by volume). Rayleigh and Ramsay isolated and identified the gas in 1894. Like the rest of the noble gases, it is colorless, tasteless and odorless. The name for argon is taken from the Greek argos for "inactive". For years argon has been used in ordinary incandescent light bulbs to replace the oxygen that would otherwise shorten the lifetime of the filament. It is used in some types of welding where active atmospheric gases would interfere with the process.

Argon is also used in various types of "black lights" or UV lamps since excitation of the gas produces a significant amount of ultraviolet radiation. A few curious compounds have been made with argon but they are not very stable. Additional Information About Argon Named from the Greek kryptos or "hidden", krypton is neither green nor a solid material that can defeat Superman. Rather it is another noble gas discovered in 1898 by Ramsay and Travers. It ranks sixth in abundance in the atmosphere. Krypton gas is used in various kinds of lights, from small bright flashlight bulbs to special strobe lights for airport runways. As with the other noble gases, krypton is isolated from the air by liquefaction. One of the naturally occurring non-radioactive isotopes of krypton, Kr-86 (17.3%) is used as the basis for the current international definition of the meter. One meter is 1,650,762.73 wavelengths of the red-orange spectral line of krypton-86.

Additional Information About Krypton Also discovered by Ramsay and Travers in 1898, xenon (from the Greek xenos for "strange") is the rarest of the stable noble gases in the air. It is still recovered by liquefaction techniques and is widely used in strobe lamps. In 1962 the first noble gas compound was produced by Neil Bartlett, combining xenon, platinum and fluorine. It is now possible to produce xenon compounds in which the oxidation states range from +2 to +8(!). Additional Information About Xenon Discovered in 1900 by Friedrich Dorn, radon is a radioactive noble gas now regarded as a potential health hazard in some homes. It also has medical applications for cancer treatment. Its original name was to be niton for "shining" but it was eventually named as a derivative of radium. Radon is found in underground deposits where is it produced by uranium and radium decay. Radon fluoride (RnF) has been produced and the element glows with a yellow light in the solid state.

The Parts of the Periodic Table Lr Group 8A (or VIIIA) of the periodic table are the noble gases or inert gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). The name comes from the fact that these elements are virtually unreactive towards other elements or compounds. They are found in trace amounts in the atmosphere (in fact, 1% of the atmosphere is argon); helium is also found in natural gas deposits. In their elemental form at room temperature, the Group 8A elements are all colorless, odorless, monatomic gases. The Group 8A elements have a full octet of eight valence electrons in their highest-energy orbitals (ns2np6), so these elements have very little tendency to gain or lose electrons to form ions, or share electrons with other elements in covalent bonds. They can be forced to form compounds with other elements, but require special conditions to do so.

Xenon, krypton compounds are known (this was first accomplished by Neil Bartlett in 1962), including XeF2, XeF4, XeF6, XeOF2, XeOF4, XeO2F2, XeO3F2, XeO2F4, XeO3, XeO4, KrF2, RnF2, among others. Helium (He, Z=2). Helium is a colorless, odorless, unreactive gas which liquefies at -268.97ï¿½C (4.18 K). The name "helium" is derived from the Greek word for the Sun, helios. Helium was originally discovered on the Sun in 1868 by Pierre Janssen: his analysis of the light emitted from the Sun's corona during a solar eclipse showed that there were lines in the Sun's spectrum that were produced by a previously unknown element.

When helium was found on Earth in the late 1890's (in association with uranium ores), it was found to have the same emission spectrum as the element previously found in the Sun, indicating that it was indeed the same element. The concentration of helium in the Earth's crust is about 8 ppb, making it the 71st most abundant element; it is found in the atmosphere at a concentration of 5 ppm (by volume). It is found in some minerals, where it is produced by radioactive elements that decay by alpha particle emission (see below). Helium is the second most abundant element in the universe (23% by mass); hydrogen and helium together make up 99% of the "normal" matter of the universe. (Of course, there's also "dark matter" and "dark energy" to worry about, but that's another story.) Hydrogen, helium, and trace amounts of lithium were produced at the beginning of the Universe in the Big Bang, and became concentrated into stars by the force of gravity. The fusion of hydrogen atoms in stars to produce helium produces huge amounts of energy; the energy in sunlight is captured by plants in photosynthesis, and drives most of the chemistry of living organisms.

The most common isotope of helium, helium-4, consists of two protons and two neutrons in the nucleus, surrounded by two electrons. An alpha particle is a type of radiation emitted by some radioactive nuclei, which consists of two protons and two neutrons, having a 2+ charge; when an alpha particle is emitted by a radioactive element, it quickly picks up two electrons from its environment, becoming a helium atom. Helium is found along with some radioactive minerals that decay by alpha particle emission, however the concentration of helium in these minerals is very low. The main source of helium is from natural gas, where it is separated out from the other components by fractional distillation. Helium liquefies at 4.18 K (-268.97ï¿½C); at 2.17 K it becomes a superfluid, in which all viscosity (resistance to flow) is lost. Some materials become superconductors when immersed in liquid helium; in these materials, there is no resistance to the flow of electricity. Superconducting magnets are used for an important medical imaging technology called Magnetic Resonance Imaging (MRI), which allows images of tissues and organs to be obtained.

A related technology is used by chemists to obtain information that can be used to deduce the structures of molecules; this technique is called Nuclear Magnetic Resonance (NMR); the two technologies are basically the same, but the term "nuclear" is avoided in the medical application because of its unpleasant associations (even though there is no nuclear radiation involved). Helium is also used in blimps, where the combination of being lighter than air and nonflammable makes it much safer than hydrogen (as demonstrated in the explosion of the Hindenburg ). It is also used in deep-sea diving, since helium is less soluble in the bloodstream than nitrogen, and reduces the risk of the diver suffering nitrogen narcosis, high pressure nervous syndrome (HPNS), or the bends. Breathing helium gas causes the voice to become higher pitched because helium is less dense than air, changing the frequency of the sound waves generated in the larynx. Neon (Ne, Z=10). Neon is a colorless, odorless, unreactive gas which liquefies at -246.1ï¿½C (27.1 K).

Neon was discovered in 1898 by Sir William Ramsay (see entry on Argon below) and his assistant Morris Travers while working with a sample of krypton. The name comes from the Greek word for "new," neos. It is found in the Earth's crust at a concentration of 70 ppt, making it the 80th most abundant element; it is found in the atmosphere at a concentration of 18 ppm (by volume). Neon which is used commercially is extracted from liquid air by fractional distillation. Neon is used primarily in neon lights; stimulating neon with electricity causes it to emit an intense red light. Other noble gases are used in "neon lights" as well, to produce different colors. Neon is also used in some underwater breathing mixtures; liquid neon is used in low-temperature cooling. Argon (Ar, Z=18). Argon is a colorless, odorless, unreactive gas which liquefies at -185.8ï¿½C (87.3 K).

It is found in the Earth's crust at a concentration of 1.2 ppm (produced by the radioactive decay of potassium-40), making it the 56th most abundant element; it is found in the atmosphere at a concentration of 0.93% (by volume). Argon which is used commercially is extracted from liquid air by fractional distillation. Even though argon makes up almost 1% of the Earth's atmosphere, it was not identified until 1894 by John William Strutt, 3rd Baron Rayleigh (Nobel Prize in Physics, 1904) and Sir William Ramsay (Nobel Prize in Chemistry, 1904). Argon had been observed before (by Henry Cavendish in 1785), but it had not been identified as an element. Because of its unreactivity, it was named for the Greek word for "idle," argos. When argon was discovered, it didn't fit with the reactivities of any other element on the periodic table, and chemists realized that there might be a whole family of previously-unrecognized elements, which we now recognize as Group 8A.

Argon is used in light bulbs because it is inert to the hot metal of the bulb filament; the filament would burn out much faster in air or even pure nitrogen. It is also used in metal refining, some "neon" lights (argon produces a blue light), some food packaging (to provide an inert atmosphere to reduce spoilage), in the tires of some luxury cars in place of air, and in lasers used in eye surgery. Argon is produced by the radioactive decay of potassium-40; the potassium-40 nucleus undergoes electron capture to produce the stable argon-40 nucleus. The ratio of potassium-40 to argon-40 in some rocks can be used to determine the age of the rock. Recently, the first argon compound, argon fluorohydride (HArF), was reported , which is stable up to 27 K. (I'm waiting for hydrogen to be replaced by boron: I think a molecule that spells out "BArF" would be worth investigating. Or not.) Krypton (Kr, Z=36).

Krypton is a colorless, odorless, unreactive gas which liquefies at -153.2ï¿½C (119.9 K). It is found in the Earth's crust at a concentration of 10 ppt, making it the 81st most abundant element; it is found in the atmosphere at a concentration of 1 ppm (by volume). Krypton which is used commercially is extracted from liquid air by fractional distillation. Krypton was discovered in 1898 by Sir William Ramsay and his assistant, Morris Travers, in a sample of argon gas extracted from the atmosphere. The name "krypton" is derived from the Greek word kryptos, meaning "hidden" (which has nothing to do with the home planet of Superman). Krypton is used in some "neon" lights, producing a violet color when electricity is passed through it. Radioactive kyrypton-85 is produced in nuclear reactors and nuclear processing plants; monitoring krypton-85 in the atmosphere allowed the United States to monitor how much nuclear material the Soviet Union was using. Xenon (Ze, Z=54).

Xenon is a colorless, odorless, unreactive gas which liquefies at -111.7ï¿½C (161.4 K). It is found in the Earth's crust at a concentration of 2 ppt, making it the 83rd most abundant element; it is found in the atmosphere at a concentration of 90 ppb (by volume). Xenon which is used commercially is extracted from liquid air by fractional distillation. Xenon was also discovered by Ramsay and Travers in 1898. The name is derived from the Greek word for "stranger," xenos. Xenon lights glow with a blue light, and also emits some low-frequency ultraviolet light. Xenon lights are used in tanning beds, biocidal lamps used in food preparation, car headlights, flash lighting on cameras, strobe lights used in high-speed photography, and has been tested for use in space travel in ion-propulsion engines (such as the experimental NASA spacecraft Deep Space 1 ). Radon (Rn, Z=86).

Radon is a colorless, odorless, radioactive gas which liquefies at -61.8ï¿½C (211.3 K). It is found in the Earth's crust in only trace amounts, and is one of the ten least abundant elements; it is found in the atmosphere at a concentration of 10-9 ppt (by volume). Radon was discovered in 1900 by Friederich Ernst Dorn while investigating "radium emanation" (first observed by Marie and Pierre Curie), a gas found in sealed vessels of radium. The name is a variation on the name of the element radium. It is produced in the radioactive decay of uranium and thorium, which in a series of steps decay into radium, which then undergoes alpha-decay to produce radon. The most common isotopes of radon are radon-220 and radon-222, which have half-lives of 55.6 seconds and 3.82 days, respectively. Although chemically unreactive, when radon is produced, it can escape from the ground in the gas form, and collect in basements, or other contained areas.

Radon is an alpha-particle emitter; while alpha particles can be blocked easily, if the radon gas is inhaled, and undergoes alpha decay in the lungs, it produces an isotope of polonium, which is a solid, as are all of its decay products, some of which have half-lives of over 20 years. Having alpha-particle emitters inside the lungs leads to a greatly increased risk of lung cancer, accounting for about 10% of all reported cases of lung cancer. References John Emsley, The Elements, 3rd edition. Oxford: Clarendon Press, 1998. John Emsley, Nature's Building Blocks: An A-Z Guide to the Elements. Oxford: Oxford University Press, 2001. David L. Heiserman, Exploring Chemical Elements and their Compounds. New York: TAB Books, 1992.

It's Elemental - The Element Krypton It's Elemental Melting Point: 115.79 K (-157.36°C or -251.25°F) Boiling Point: 119.93 K (-153.22°C or -243.80°F) Density: 0.003733 grams per cubic centimeter Phase at Room Temperature: Gas Element Classification: Non-metal Period Number: 4 Group Number: 18 Group Name: Noble Gas What's in a name? From the Greek word for hidden, kryptos. Say what? Krypton is pronounced as KRIP-ton. History and Uses: Krypton was discovered on May 30, 1898 by Sir William Ramsay, a Scottish chemist, and Morris M. Travers, an English chemist, while studying liquefied air. Small amounts of liquid krypton remained behind after the more volatile components of liquid air had boiled away. The earth's atmosphere is about 0.0001% krypton. The high cost of obtaining krypton from the air has limited its practical applications.

Krypton is used in some types of photographic flashes used in high speed photography. Some fluorescent light bulbs are filled with a mixture of krypton and argon gases. Krypton gas is also combined with other gases to make luminous signs that glow with a greenish-yellow light. In 1960, the length of the meter was defined in terms of the orange-red spectral line of krypton-86, an isotope of krypton. Once thought to be completely inert, krypton is known to form a few compounds. Krypton difluoride (KrF2) is the easiest krypton compound to make and gram amounts of it have been produced. For those that are curious, pictures of krypton gas and krypton plasma can be found in the Questions and Answers section of this site.

Estimated Crustal Abundance: 1×10-4 milligrams per kilogram Estimated Oceanic Abundance: 2.1×10-4 milligrams per liter Number of Stable Isotopes: 5 ( View all isotope data ) Ionization Energy: 14.000 eV Krypton, Chemical Element - uses, elements, metal, gas, number, name, symbol, mass Photo by: OlesiaRu Overview Krypton was one of three noble gases discovered in 1898 by Scottish chemist and physicist Sir William Ramsay (1852-1916) and English chemist Morris William Travers (1872-1961). Ramsay and Travers discovered the gases by allowing liquid air to evaporate. As it did so, each of the gases that make up normal air boiled off, one at a time. Three of those gases—krypton, xenon, and neon, were discovered for the first time this way. The term noble gas refers to elements in Group 18 (VIIIA) of the periodic table. The periodic table is a chart that shows how chemical elements are related to each other.

These gases have been given the name "noble" because they act as if they are "too arrogant" to react with other elements. Until the 1960s, no compound of these gases was known. Since they are so inactive, they are also called the inert gases. Inert means inactive. SYMBOL PRONUNCIATION KRIP-ton Krypton has relatively few commercial uses. All of them involve lighting systems in one way or another. Discovery and naming By 1898, two members of the noble gas family had been discovered. They were helium (atomic number 2) and argon (atomic number 18). But no other elements in the family had been found. The periodic table contained empty boxes between helium and argon and below argon. The missing noble gases had atomic numbers 10, 36, 54, and 86. Chemists think of empty boxes in the periodic table as "elements waiting to be discovered." Since the two known noble elements, helium and argon, are both gases, Ramsay and Travers hoped the missing elements were also gases. And if they were, they might be found in air.

The problem was that air had already been carefully analyzed and found to be about 99.95 percent oxygen , nitrogen , and argon. Was it possible that the missing gases were in the last 0.05 percent of air? To answer the question, the chemists worked not with air itself, but with liquid air. Air becomes liquid simply by cooling it far enough. The colder air becomes, the more gases within it turn into liquids. At -182.96°C (-297.33°F), oxygen changes from a gas into a liquid. At -195.79°C (-320.42°F), nitrogen changes from a gas into a liquid. And so on. Eventually, all the gases in air can be made to liquefy (change into a liquid). But the reverse process also takes place. Suppose a container of liquid air holds 100 liters. The liquid air will warm up slowly. When its temperature reaches -195.79°C, liquid nitrogen changes back to a gas. Since about 78 percent of air is nitrogen, only 22 percent of the original liquid air (22 liters) will be left.

When the temperature reaches -182.96°C, oxygen changes from a liquid back to a gas. Since oxygen makes up 21 percent of air, another 21 percent (21 liters) of the liquid air will evaporate. The work of Ramsay and Travers was very difficult, however, because the gases they were looking for are not abundant in air. Krypton, for example, makes up only about 0.000114 percent of air. For every 100 liters of liquid air, there would be only 0.00011, or about one-tenth of a milliliter of krypton. A tenth of a milliliter is about a drop. So Ramsay and Travers—although they didn't know it—were looking for one drop of krypton in 100 liters of liquid air! Amazingly, they found it. The discovery of these three gases was a great credit to their skills as researchers. They suggested the name krypton for the new element. The name was taken from the Greek word kryptos for "hidden." Physical properties Krypton is a colorless, odorless gas.

It has a boiling point of -152.9°C (-243.2°F) and a density of 3.64 grams per liter. That makes krypton about 2.8 times as dense as air. "Look, up in the sky! It's a bird! It's a plane.... T he famous cartoon character Superman has many super powers. Everybody knows that. He's the Man of Steel. He has X-ray vision. His hearing is so good, he can tune in on one voice in a crowded city. And, of course: He's faster than a speeding bullet! More powerful than a locomotive! Able to leap tall buildings in a single bound! But there's one substance that weakens Superman: kryptonite! If exposed to kryptonite. Superman experiences pain and loses his super powers. If exposed for too long, he can even die. Kryptonite, of course, is purely fictional. Despite the similarity in names, kryptonite has nothing to do with element 36, krypton. According to cartoon legend, Superman came from the planet Krypton.

Kal-El, as he was originally known, was placed in a spaceship by his parents, moments before the planet exploded. Unfortunately, as the young Superman blasted away from Krypton, a piece of kryptonite got stuck on the spaceship. The same terrible forces that caused the planet to explode, also had created the deadly kryptonite. And, as Superman would later find out, arch-villains always seem to get their hands on this green glowing rock! Aside from the fictitious nature of kryptonite, there is another difference between it and krypton. Kryptonite is a rock—one that can cause great harm to, well, one person anyway. Krypton is an inert gas that has no effect on anything. Chemical properties For many years, krypton was thought to be completely inert. Then, in the early 1960s, it was found to be possible to make certain compounds of the element. English chemist Neil Bartlett (1932-) found ways to combine noble gases with the most active element of all, fluorine.

In 1963, the first krypton compounds were made—krypton difluoride (KrF 2 ) and krypton tetrafluoride (KrF 4 ). Other compounds of krypton have also been made since that time. However, these have no commercial uses. They are only laboratory curiosities. Occurrence in nature The abundance of krypton in the atmosphere is thought to be about 0.000108 to 0.000114 percent. The element is also formed in the Earth's crust when uranium and other radioactive elements break down. The amount in the Earth's crust is too small to estimate, however. Isotopes Six naturally occurring isotopes of krypton exist. They are krypton-78, krypton-80, krypton-82, krypton-83, krypton-84, and krypton-86. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number.

The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope. At least sixteen radioactive isotopes of krypton are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive. One radioactive isotope of krypton is used commercially, krypton-85. It can be combined with phosphors to produce materials that shine in the dark. A phosphor is a material that shines when struck by electrons. Radiation given off by krypton-85 strikes the phosphor. The phosphor then gives off light. The same isotope is also used for detecting leaks in a container. The radioactive gas is placed inside the container to be tested. Since the gas is inert, krypton will not react with anything else in the container. But if the container has a leak, some radioactive krypton-85 will escape. The isotope can be detected with special devices for detecting radiation.

Krypton-85 is also used to study the flow of blood in the human body. It is inhaled as a gas, and then absorbed by the blood. It travels through the bloodstream and the heart along with the blood. Its pathway can be followed by a technician who holds a detection device over the patient's body. The device shows where the radioactive material is going and how fast it is moving. A doctor can determine whether this behavior is normal or not. How long is a meter? T he meter is the standard unit of length in the metric system. It was first defined in 1791. As part of the great changes brought by the French Revolution, an entirely new system of measurement was created: the metric system. At first, the meter was defined in a very simple way. It was the distance between two lines scratched into a metal bar kept outside Paris. For many years, that definition was satisfactory for most purposes. Of course, it created a problem. Suppose someone in the United States was in the business of making meter sticks. That person would have to travel to Paris to make a copy of the official meter. Then the copy would have to be used to make other copies. The chances for error in this process are tremendous.

In 1960, scientists had another idea. They suggested using light produced by hot krypton as the standard of length. Here is how that standard was developed: When an element is heated, it absorbs energy from the heat. The atoms present in the element are in an "excited," or energetic, state. Atoms normally do not remain in an excited state very long. They give off the energy they just absorbed and return to their normal, "unexcited" state. The energy they give off can take different forms. One of those forms is light. The kind of light given off is different for each element and for each isotope. The light usually consists of a series of very bright lines called a spectrum. The number and color of the lines produced is specific to each element and isotope. When one isotope of krypton, krypton-86, is heated, it gives off a very clear, distinct, bright line with a reddish-orange color. Scientists decided to define the meter in terms of that line. They said that a meter is 1,650,763.73 times the width of that line. This standard had many advantages.

For one thing, almost anyone anywhere could find the official length of a meter. All one needed was the equipment to heat a sample of krypton-86. Then one had to look for the reddish-orange line produced. The length of the meter, then, was 1,650,763.73 times the width of that line. This definition for the meter lasted only until 1983. Scientists then decided to define a meter by how fast light travels in a vacuum. This system is even more exact than the one based on krypton-86. Extraction Krypton is still obtained by allowing liquid air to evaporate. Uses The only commercial uses of krypton are in various kinds of lamps. When an electric current is passed through krypton gas, it gives off a very bright light. Perhaps the most common application of this principle is in airport runway lights. These lights are so bright that they can be seen even in foggy conditions for distances up to 300 meters (1,000 feet). The lights do not burn continuously. Instead, they send out very brief pulses of light. The pulses last no more than about 10 microseconds (10 millionths of a second).

They flash on and off about 40 times per minute. Krypton is also used in slide and movie projectors. Krypton gas is also used in making "neon" lights. Neon lights are colored lights often used in advertising. They are similar to fluorescent light bulbs. But they give off a colored light because of the gas they contain. Some neon lights do contain the gas neon, but others contain other noble gases. A neon light filled with krypton, for example, glows yellow. Compounds Compounds of krypton have been prepared in the laboratory but do not exist in nature. The synthetic (artificial) compounds are used for research purposes only. Although neon lights sometimes do include neon, krypton is often the gas used. Health effects Krypton Krypton Krypton is a noble-gas, which has atomic number 18.Its name comes from the greek word for hidden, Kryptos. Krypton is Discovered Krypton was discovered by Sir William Ramsay, who was scottish, and Morris M. Travers, who was english, while they were studying liquefied air. Krypton and Other Elements Krypton mixes with Argon as a source of energy saving fluorescent gas lamps.

Tpgether with Xenon, it creates a birghter light which is used to allow higher temperatures. Krypton in the World In the atmosphere, krypton's concentration is 1 ppm. The amount of it in space is uncertain, but the first measurements suggested that it was an overabundance. Curiosities Krypton can be used to discover the presence of secret nuclear weapons and its research facilities. Also, krypton-fluorine lasers produce pulses with 500 times the power of the US. Numbers Everywhere Crustal Abundance: 1×10-4 milligrams per kilogram Oceanic Abundance: 2.1×10-4 milligrams per liter Stable Isotopes: 5 Ionization energy: 14.000 eV Oxidation Sate: 0 State Krypton is a colorless and odorless gas, which is inert to everything but fluorine. One of the rarest gases in the earth's atmosphere. Krypton 86 Krypton 86 is an isotope that has a line in its atomic spectrum which is now the standard measure of length.

One meter is exactly 1,650,763.73 wavelengths of this line. Search

Question: Which inert gas takes its name from the Greek for 'hidden'?
Answer: KRYPTON